/**
 * @file
 *
 * IPv6 layer.
 */

/*
 * Copyright (c) 2010 Inico Technologies Ltd.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Ivan Delamer <delamer@inicotech.com>
 *
 *
 * Please coordinate changes and requests with Ivan Delamer
 * <delamer@inicotech.com>
 */

#include "lwip/opt.h"

#if LWIP_IPV6  /* don't build if not configured for use in lwipopts.h */

#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/netif.h"
#include "lwip/ip.h"
#include "lwip/ip6.h"
#include "lwip/ip6_addr.h"
#include "lwip/ip6_frag.h"
#include "lwip/icmp6.h"
#include "lwip/raw.h"
#include "lwip/udp.h"
#include "lwip/priv/tcp_priv.h"
#include "lwip/dhcp6.h"
#include "lwip/nd6.h"
#include "lwip/mld6.h"
#include "lwip/debug.h"
#include "lwip/stats.h"

#ifdef LWIP_HOOK_FILENAME
	#include LWIP_HOOK_FILENAME
#endif

/**
 * Finds the appropriate network interface for a given IPv6 address. It tries to select
 * a netif following a sequence of heuristics:
 * 1) if there is only 1 netif, return it
 * 2) if the destination is a link-local address, try to match the src address to a netif.
 *    this is a tricky case because with multiple netifs, link-local addresses only have
 *    meaning within a particular subnet/link.
 * 3) tries to match the destination subnet to a configured address
 * 4) tries to find a router
 * 5) tries to match the source address to the netif
 * 6) returns the default netif, if configured
 *
 * @param src the source IPv6 address, if known
 * @param dest the destination IPv6 address for which to find the route
 * @return the netif on which to send to reach dest
 */
struct netif*
ip6_route(const ip6_addr_t* src, const ip6_addr_t* dest)
{
	struct netif* netif;
	s8_t i;

	/* If single netif configuration, fast return. */
	if((netif_list != NULL) && (netif_list->next == NULL)) {
		if(!netif_is_up(netif_list) || !netif_is_link_up(netif_list)) {
			return NULL;
		}

		return netif_list;
	}

	/* Special processing for link-local addresses. */
	if(ip6_addr_islinklocal(dest)) {
		if(ip6_addr_isany(src)) {
			/* Use default netif, if Up. */
			if(netif_default == NULL || !netif_is_up(netif_default) ||
			        !netif_is_link_up(netif_default)) {
				return NULL;
			}

			return netif_default;
		}

		/* Try to find the netif for the source address, checking that link is up. */
		for(netif = netif_list; netif != NULL; netif = netif->next) {
			if(!netif_is_up(netif) || !netif_is_link_up(netif)) {
				continue;
			}

			for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
				if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
				        ip6_addr_cmp(src, netif_ip6_addr(netif, i))) {
					return netif;
				}
			}
		}

		/* netif not found, use default netif, if up */
		if(netif_default == NULL || !netif_is_up(netif_default) ||
		        !netif_is_link_up(netif_default)) {
			return NULL;
		}

		return netif_default;
	}

	/* we come here for non-link-local addresses */
#ifdef LWIP_HOOK_IP6_ROUTE
	netif = LWIP_HOOK_IP6_ROUTE(src, dest);

	if(netif != NULL) {
		return netif;
	}

#endif

	/* See if the destination subnet matches a configured address. */
	for(netif = netif_list; netif != NULL; netif = netif->next) {
		if(!netif_is_up(netif) || !netif_is_link_up(netif)) {
			continue;
		}

		for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
			if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
			        ip6_addr_netcmp(dest, netif_ip6_addr(netif, i))) {
				return netif;
			}
		}
	}

	/* Get the netif for a suitable router. */
	netif = nd6_find_route(dest);

	if((netif != NULL) && netif_is_up(netif) && netif_is_link_up(netif)) {
		return netif;
	}

	/* try with the netif that matches the source address. */
	if(!ip6_addr_isany(src)) {
		for(netif = netif_list; netif != NULL; netif = netif->next) {
			if(!netif_is_up(netif) || !netif_is_link_up(netif)) {
				continue;
			}

			for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
				if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
				        ip6_addr_cmp(src, netif_ip6_addr(netif, i))) {
					return netif;
				}
			}
		}
	}

#if LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF

	/* loopif is disabled, loopback traffic is passed through any netif */
	if(ip6_addr_isloopback(dest)) {
		/* don't check for link on loopback traffic */
		if(netif_default != NULL && netif_is_up(netif_default)) {
			return netif_default;
		}

		/* default netif is not up, just use any netif for loopback traffic */
		for(netif = netif_list; netif != NULL; netif = netif->next) {
			if(netif_is_up(netif)) {
				return netif;
			}
		}

		return NULL;
	}

#endif /* LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF */

	/* no matching netif found, use default netif, if up */
	if((netif_default == NULL) || !netif_is_up(netif_default) || !netif_is_link_up(netif_default)) {
		return NULL;
	}

	return netif_default;
}

/**
 * @ingroup ip6
 * Select the best IPv6 source address for a given destination
 * IPv6 address. Loosely follows RFC 3484. "Strong host" behavior
 * is assumed.
 *
 * @param netif the netif on which to send a packet
 * @param dest the destination we are trying to reach
 * @return the most suitable source address to use, or NULL if no suitable
 *         source address is found
 */
const ip_addr_t*
ip6_select_source_address(struct netif* netif, const ip6_addr_t* dest)
{
	const ip_addr_t* src = NULL;
	u8_t i;

	/* If dest is link-local, choose a link-local source. */
	if(ip6_addr_islinklocal(dest) || ip6_addr_ismulticast_linklocal(dest) || ip6_addr_ismulticast_iflocal(dest)) {
		for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
			if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
			        ip6_addr_islinklocal(netif_ip6_addr(netif, i))) {
				return netif_ip_addr6(netif, i);
			}
		}
	}

	/* Choose a site-local with matching prefix. */
	if(ip6_addr_issitelocal(dest) || ip6_addr_ismulticast_sitelocal(dest)) {
		for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
			if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
			        ip6_addr_issitelocal(netif_ip6_addr(netif, i)) &&
			        ip6_addr_netcmp(dest, netif_ip6_addr(netif, i))) {
				return netif_ip_addr6(netif, i);
			}
		}
	}

	/* Choose a unique-local with matching prefix. */
	if(ip6_addr_isuniquelocal(dest) || ip6_addr_ismulticast_orglocal(dest)) {
		for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
			if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
			        ip6_addr_isuniquelocal(netif_ip6_addr(netif, i)) &&
			        ip6_addr_netcmp(dest, netif_ip6_addr(netif, i))) {
				return netif_ip_addr6(netif, i);
			}
		}
	}

	/* Choose a global with best matching prefix. */
	if(ip6_addr_isglobal(dest) || ip6_addr_ismulticast_global(dest)) {
		for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
			if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
			        ip6_addr_isglobal(netif_ip6_addr(netif, i))) {
				if(src == NULL) {
					src = netif_ip_addr6(netif, i);
				} else {
					/* Replace src only if we find a prefix match. */
					/* @todo find longest matching prefix. */
					if((!(ip6_addr_netcmp(ip_2_ip6(src), dest))) &&
					        ip6_addr_netcmp(netif_ip6_addr(netif, i), dest)) {
						src = netif_ip_addr6(netif, i);
					}
				}
			}
		}

		if(src != NULL) {
			return src;
		}
	}

	/* Last resort: see if arbitrary prefix matches. */
	for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
		if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
		        ip6_addr_netcmp(dest, netif_ip6_addr(netif, i))) {
			return netif_ip_addr6(netif, i);
		}
	}

	return NULL;
}

#if LWIP_IPV6_FORWARD
/**
 * Forwards an IPv6 packet. It finds an appropriate route for the
 * packet, decrements the HL value of the packet, and outputs
 * the packet on the appropriate interface.
 *
 * @param p the packet to forward (p->payload points to IP header)
 * @param iphdr the IPv6 header of the input packet
 * @param inp the netif on which this packet was received
 */
static void
ip6_forward(struct pbuf* p, struct ip6_hdr* iphdr, struct netif* inp)
{
	struct netif* netif;

	/* do not forward link-local or loopback addresses */
	if(ip6_addr_islinklocal(ip6_current_dest_addr()) ||
	        ip6_addr_isloopback(ip6_current_dest_addr())) {
		LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: not forwarding link-local address.\n"));
		IP6_STATS_INC(ip6.rterr);
		IP6_STATS_INC(ip6.drop);
		return;
	}

	/* Find network interface where to forward this IP packet to. */
	netif = ip6_route(IP6_ADDR_ANY6, ip6_current_dest_addr());

	if(netif == NULL) {
		LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: no route for %"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F"\n",
		                        IP6_ADDR_BLOCK1(ip6_current_dest_addr()),
		                        IP6_ADDR_BLOCK2(ip6_current_dest_addr()),
		                        IP6_ADDR_BLOCK3(ip6_current_dest_addr()),
		                        IP6_ADDR_BLOCK4(ip6_current_dest_addr()),
		                        IP6_ADDR_BLOCK5(ip6_current_dest_addr()),
		                        IP6_ADDR_BLOCK6(ip6_current_dest_addr()),
		                        IP6_ADDR_BLOCK7(ip6_current_dest_addr()),
		                        IP6_ADDR_BLOCK8(ip6_current_dest_addr())));
#if LWIP_ICMP6

		/* Don't send ICMP messages in response to ICMP messages */
		if(IP6H_NEXTH(iphdr) != IP6_NEXTH_ICMP6) {
			icmp6_dest_unreach(p, ICMP6_DUR_NO_ROUTE);
		}

#endif /* LWIP_ICMP6 */
		IP6_STATS_INC(ip6.rterr);
		IP6_STATS_INC(ip6.drop);
		return;
	}

	/* Do not forward packets onto the same network interface on which
	 * they arrived. */
	if(netif == inp) {
		LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: not bouncing packets back on incoming interface.\n"));
		IP6_STATS_INC(ip6.rterr);
		IP6_STATS_INC(ip6.drop);
		return;
	}

	/* decrement HL */
	IP6H_HOPLIM_SET(iphdr, IP6H_HOPLIM(iphdr) - 1);

	/* send ICMP6 if HL == 0 */
	if(IP6H_HOPLIM(iphdr) == 0) {
#if LWIP_ICMP6

		/* Don't send ICMP messages in response to ICMP messages */
		if(IP6H_NEXTH(iphdr) != IP6_NEXTH_ICMP6) {
			icmp6_time_exceeded(p, ICMP6_TE_HL);
		}

#endif /* LWIP_ICMP6 */
		IP6_STATS_INC(ip6.drop);
		return;
	}

	if(netif->mtu && (p->tot_len > netif->mtu)) {
#if LWIP_ICMP6

		/* Don't send ICMP messages in response to ICMP messages */
		if(IP6H_NEXTH(iphdr) != IP6_NEXTH_ICMP6) {
			icmp6_packet_too_big(p, netif->mtu);
		}

#endif /* LWIP_ICMP6 */
		IP6_STATS_INC(ip6.drop);
		return;
	}

	LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: forwarding packet to %"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F"\n",
	                        IP6_ADDR_BLOCK1(ip6_current_dest_addr()),
	                        IP6_ADDR_BLOCK2(ip6_current_dest_addr()),
	                        IP6_ADDR_BLOCK3(ip6_current_dest_addr()),
	                        IP6_ADDR_BLOCK4(ip6_current_dest_addr()),
	                        IP6_ADDR_BLOCK5(ip6_current_dest_addr()),
	                        IP6_ADDR_BLOCK6(ip6_current_dest_addr()),
	                        IP6_ADDR_BLOCK7(ip6_current_dest_addr()),
	                        IP6_ADDR_BLOCK8(ip6_current_dest_addr())));

	/* transmit pbuf on chosen interface */
	netif->output_ip6(netif, p, ip6_current_dest_addr());
	IP6_STATS_INC(ip6.fw);
	IP6_STATS_INC(ip6.xmit);
	return;
}
#endif /* LWIP_IPV6_FORWARD */

/**
 * This function is called by the network interface device driver when
 * an IPv6 packet is received. The function does the basic checks of the
 * IP header such as packet size being at least larger than the header
 * size etc. If the packet was not destined for us, the packet is
 * forwarded (using ip6_forward).
 *
 * Finally, the packet is sent to the upper layer protocol input function.
 *
 * @param p the received IPv6 packet (p->payload points to IPv6 header)
 * @param inp the netif on which this packet was received
 * @return ERR_OK if the packet was processed (could return ERR_* if it wasn't
 *         processed, but currently always returns ERR_OK)
 */
err_t
ip6_input(struct pbuf* p, struct netif* inp)
{
	struct ip6_hdr* ip6hdr;
	struct netif* netif;
	u8_t nexth;
	u16_t hlen; /* the current header length */
	u8_t i;
#if 0 /*IP_ACCEPT_LINK_LAYER_ADDRESSING*/
	@todo
	int check_ip_src = 1;
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */

	IP6_STATS_INC(ip6.recv);

	/* identify the IP header */
	ip6hdr = (struct ip6_hdr*)p->payload;

	if(IP6H_V(ip6hdr) != 6) {
		LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_WARNING, ("IPv6 packet dropped due to bad version number %"U32_F"\n",
		            IP6H_V(ip6hdr)));
		pbuf_free(p);
		IP6_STATS_INC(ip6.err);
		IP6_STATS_INC(ip6.drop);
		return ERR_OK;
	}

#ifdef LWIP_HOOK_IP6_INPUT

	if(LWIP_HOOK_IP6_INPUT(p, inp)) {
		/* the packet has been eaten */
		return ERR_OK;
	}

#endif

	/* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */
	if((IP6_HLEN > p->len) || ((IP6H_PLEN(ip6hdr) + IP6_HLEN) > p->tot_len)) {
		if(IP6_HLEN > p->len) {
			LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
			            ("IPv6 header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet dropped.\n",
			             (u16_t)IP6_HLEN, p->len));
		}

		if((IP6H_PLEN(ip6hdr) + IP6_HLEN) > p->tot_len) {
			LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
			            ("IPv6 (plen %"U16_F") is longer than pbuf (len %"U16_F"), IP packet dropped.\n",
			             (u16_t)(IP6H_PLEN(ip6hdr) + IP6_HLEN), p->tot_len));
		}

		/* free (drop) packet pbufs */
		pbuf_free(p);
		IP6_STATS_INC(ip6.lenerr);
		IP6_STATS_INC(ip6.drop);
		return ERR_OK;
	}

	/* Trim pbuf. This should have been done at the netif layer,
	 * but we'll do it anyway just to be sure that its done. */
	pbuf_realloc(p, IP6_HLEN + IP6H_PLEN(ip6hdr));

	/* copy IP addresses to aligned ip6_addr_t */
	ip_addr_copy_from_ip6(ip_data.current_iphdr_dest, ip6hdr->dest);
	ip_addr_copy_from_ip6(ip_data.current_iphdr_src, ip6hdr->src);

	/* Don't accept virtual IPv4 mapped IPv6 addresses.
	 * Don't accept multicast source addresses. */
	if(ip6_addr_isipv4mappedipv6(ip_2_ip6(&ip_data.current_iphdr_dest)) ||
	        ip6_addr_isipv4mappedipv6(ip_2_ip6(&ip_data.current_iphdr_src)) ||
	        ip6_addr_ismulticast(ip_2_ip6(&ip_data.current_iphdr_src))) {
		IP6_STATS_INC(ip6.err);
		IP6_STATS_INC(ip6.drop);
		return ERR_OK;
	}

	/* current header pointer. */
	ip_data.current_ip6_header = ip6hdr;

	/* In netif, used in case we need to send ICMPv6 packets back. */
	ip_data.current_netif = inp;
	ip_data.current_input_netif = inp;

	/* match packet against an interface, i.e. is this packet for us? */
	if(ip6_addr_ismulticast(ip6_current_dest_addr())) {
		/* Always joined to multicast if-local and link-local all-nodes group. */
		if(ip6_addr_isallnodes_iflocal(ip6_current_dest_addr()) ||
		        ip6_addr_isallnodes_linklocal(ip6_current_dest_addr())) {
			netif = inp;
		}

#if LWIP_IPV6_MLD
		else if(mld6_lookfor_group(inp, ip6_current_dest_addr())) {
			netif = inp;
		}

#else /* LWIP_IPV6_MLD */
		else if(ip6_addr_issolicitednode(ip6_current_dest_addr())) {
			/* Filter solicited node packets when MLD is not enabled
			 * (for Neighbor discovery). */
			netif = NULL;

			for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
				if(ip6_addr_isvalid(netif_ip6_addr_state(inp, i)) &&
				        ip6_addr_cmp_solicitednode(ip6_current_dest_addr(), netif_ip6_addr(inp, i))) {
					netif = inp;
					LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: solicited node packet accepted on interface %c%c\n",
					                        netif->name[0], netif->name[1]));
					break;
				}
			}
		}

#endif /* LWIP_IPV6_MLD */
		else {
			netif = NULL;
		}
	} else {
		/* start trying with inp. if that's not acceptable, start walking the
		   list of configured netifs.
		   'first' is used as a boolean to mark whether we started walking the list */
		int first = 1;
		netif = inp;

		do {
			/* interface is up? */
			if(netif_is_up(netif)) {
				/* unicast to this interface address? address configured? */
				for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
					if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
					        ip6_addr_cmp(ip6_current_dest_addr(), netif_ip6_addr(netif, i))) {
						/* exit outer loop */
						goto netif_found;
					}
				}
			}

			if(first) {
				if(ip6_addr_islinklocal(ip6_current_dest_addr())
#if !LWIP_NETIF_LOOPBACK || LWIP_HAVE_LOOPIF
				        || ip6_addr_isloopback(ip6_current_dest_addr())
#endif /* !LWIP_NETIF_LOOPBACK || LWIP_HAVE_LOOPIF */
				  ) {
					/* Do not match link-local addresses to other netifs. The loopback
					 * address is to be considered link-local and packets to it should be
					 * dropped on other interfaces, as per RFC 4291 Sec. 2.5.3. This
					 * requirement cannot be implemented in the case that loopback
					 * traffic is sent across a non-loopback interface, however.
					 */
					netif = NULL;
					break;
				}

				first = 0;
				netif = netif_list;
			} else {
				netif = netif->next;
			}

			if(netif == inp) {
				netif = netif->next;
			}
		} while(netif != NULL);

netif_found:
		LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet accepted on interface %c%c\n",
		                        netif ? netif->name[0] : 'X', netif ? netif->name[1] : 'X'));
	}

	/* "::" packet source address? (used in duplicate address detection) */
	if(ip6_addr_isany(ip6_current_src_addr()) &&
	        (!ip6_addr_issolicitednode(ip6_current_dest_addr()))) {
		/* packet source is not valid */
		/* free (drop) packet pbufs */
		LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with src ANY_ADDRESS dropped\n"));
		pbuf_free(p);
		IP6_STATS_INC(ip6.drop);
		goto ip6_input_cleanup;
	}

	/* packet not for us? */
	if(netif == NULL) {
		/* packet not for us, route or discard */
		LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_TRACE, ("ip6_input: packet not for us.\n"));
#if LWIP_IPV6_FORWARD

		/* non-multicast packet? */
		if(!ip6_addr_ismulticast(ip6_current_dest_addr())) {
			/* try to forward IP packet on (other) interfaces */
			ip6_forward(p, ip6hdr, inp);
		}

#endif /* LWIP_IPV6_FORWARD */
		pbuf_free(p);
		goto ip6_input_cleanup;
	}

	/* current netif pointer. */
	ip_data.current_netif = netif;

	/* Save next header type. */
	nexth = IP6H_NEXTH(ip6hdr);

	/* Init header length. */
	hlen = ip_data.current_ip_header_tot_len = IP6_HLEN;

	/* Move to payload. */
	pbuf_header(p, -IP6_HLEN);

	/* Process known option extension headers, if present. */
	while(nexth != IP6_NEXTH_NONE) {
		switch(nexth) {
			case IP6_NEXTH_HOPBYHOP:
				LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Hop-by-Hop options header\n"));
				/* Get next header type. */
				nexth = *((u8_t*)p->payload);

				/* Get the header length. */
				hlen = 8 * (1 + * ((u8_t*)p->payload + 1));
				ip_data.current_ip_header_tot_len += hlen;

				/* Skip over this header. */
				if(hlen > p->len) {
					LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
					            ("IPv6 options header (hlen %"U16_F") does not fit in first pbuf (len %"U16_F"), IPv6 packet dropped.\n",
					             hlen, p->len));
					/* free (drop) packet pbufs */
					pbuf_free(p);
					IP6_STATS_INC(ip6.lenerr);
					IP6_STATS_INC(ip6.drop);
					goto ip6_input_cleanup;
				}

				pbuf_header(p, -(s16_t)hlen);
				break;

			case IP6_NEXTH_DESTOPTS:
				LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Destination options header\n"));
				/* Get next header type. */
				nexth = *((u8_t*)p->payload);

				/* Get the header length. */
				hlen = 8 * (1 + * ((u8_t*)p->payload + 1));
				ip_data.current_ip_header_tot_len += hlen;

				/* Skip over this header. */
				if(hlen > p->len) {
					LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
					            ("IPv6 options header (hlen %"U16_F") does not fit in first pbuf (len %"U16_F"), IPv6 packet dropped.\n",
					             hlen, p->len));
					/* free (drop) packet pbufs */
					pbuf_free(p);
					IP6_STATS_INC(ip6.lenerr);
					IP6_STATS_INC(ip6.drop);
					goto ip6_input_cleanup;
				}

				pbuf_header(p, -(s16_t)hlen);
				break;

			case IP6_NEXTH_ROUTING:
				LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Routing header\n"));
				/* Get next header type. */
				nexth = *((u8_t*)p->payload);

				/* Get the header length. */
				hlen = 8 * (1 + * ((u8_t*)p->payload + 1));
				ip_data.current_ip_header_tot_len += hlen;

				/* Skip over this header. */
				if(hlen > p->len) {
					LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
					            ("IPv6 options header (hlen %"U16_F") does not fit in first pbuf (len %"U16_F"), IPv6 packet dropped.\n",
					             hlen, p->len));
					/* free (drop) packet pbufs */
					pbuf_free(p);
					IP6_STATS_INC(ip6.lenerr);
					IP6_STATS_INC(ip6.drop);
					goto ip6_input_cleanup;
				}

				pbuf_header(p, -(s16_t)hlen);
				break;

			case IP6_NEXTH_FRAGMENT: {
				struct ip6_frag_hdr* frag_hdr;
				LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Fragment header\n"));

				frag_hdr = (struct ip6_frag_hdr*)p->payload;

				/* Get next header type. */
				nexth = frag_hdr->_nexth;

				/* Fragment Header length. */
				hlen = 8;
				ip_data.current_ip_header_tot_len += hlen;

				/* Make sure this header fits in current pbuf. */
				if(hlen > p->len) {
					LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
					            ("IPv6 options header (hlen %"U16_F") does not fit in first pbuf (len %"U16_F"), IPv6 packet dropped.\n",
					             hlen, p->len));
					/* free (drop) packet pbufs */
					pbuf_free(p);
					IP6_FRAG_STATS_INC(ip6_frag.lenerr);
					IP6_FRAG_STATS_INC(ip6_frag.drop);
					goto ip6_input_cleanup;
				}

				/* Offset == 0 and more_fragments == 0? */
				if((frag_hdr->_fragment_offset&
				        PP_HTONS(IP6_FRAG_OFFSET_MASK | IP6_FRAG_MORE_FLAG)) == 0) {
					/* This is a 1-fragment packet, usually a packet that we have
					 * already reassembled. Skip this header anc continue. */
					pbuf_header(p, -(s16_t)hlen);
				} else {
#if LWIP_IPV6_REASS

					/* reassemble the packet */
					p = ip6_reass(p);

					/* packet not fully reassembled yet? */
					if(p == NULL) {
						goto ip6_input_cleanup;
					}

					/* Returned p point to IPv6 header.
					 * Update all our variables and pointers and continue. */
					ip6hdr = (struct ip6_hdr*)p->payload;
					nexth = IP6H_NEXTH(ip6hdr);
					hlen = ip_data.current_ip_header_tot_len = IP6_HLEN;
					pbuf_header(p, -IP6_HLEN);

#else /* LWIP_IPV6_REASS */
					/* free (drop) packet pbufs */
					LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Fragment header dropped (with LWIP_IPV6_REASS==0)\n"));
					pbuf_free(p);
					IP6_STATS_INC(ip6.opterr);
					IP6_STATS_INC(ip6.drop);
					goto ip6_input_cleanup;
#endif /* LWIP_IPV6_REASS */
				}

				break;
			}

			default:
				goto options_done;
				break;
		}
	}

options_done:

	/* p points to IPv6 header again. */
	pbuf_header_force(p, (s16_t)ip_data.current_ip_header_tot_len);

	/* send to upper layers */
	LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: \n"));
	ip6_debug_print(p);
	LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len));

#if LWIP_RAW

	/* raw input did not eat the packet? */
	if(raw_input(p, inp) == 0)
#endif /* LWIP_RAW */
	{
		switch(nexth) {
			case IP6_NEXTH_NONE:
				pbuf_free(p);
				break;
#if LWIP_UDP

			case IP6_NEXTH_UDP:
#if LWIP_UDPLITE
			case IP6_NEXTH_UDPLITE:
#endif /* LWIP_UDPLITE */
				/* Point to payload. */
				pbuf_header(p, -(s16_t)ip_data.current_ip_header_tot_len);
				udp_input(p, inp);
				break;
#endif /* LWIP_UDP */
#if LWIP_TCP

			case IP6_NEXTH_TCP:
				/* Point to payload. */
				pbuf_header(p, -(s16_t)ip_data.current_ip_header_tot_len);
				tcp_input(p, inp);
				break;
#endif /* LWIP_TCP */
#if LWIP_ICMP6

			case IP6_NEXTH_ICMP6:
				/* Point to payload. */
				pbuf_header(p, -(s16_t)ip_data.current_ip_header_tot_len);
				icmp6_input(p, inp);
				break;
#endif /* LWIP_ICMP */

			default:
#if LWIP_ICMP6

				/* send ICMP parameter problem unless it was a multicast or ICMPv6 */
				if((!ip6_addr_ismulticast(ip6_current_dest_addr())) &&
				        (IP6H_NEXTH(ip6hdr) != IP6_NEXTH_ICMP6)) {
					icmp6_param_problem(p, ICMP6_PP_HEADER, ip_data.current_ip_header_tot_len - hlen);
				}

#endif /* LWIP_ICMP */
				LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip6_input: Unsupported transport protocol %"U16_F"\n", (u16_t)IP6H_NEXTH(ip6hdr)));
				pbuf_free(p);
				IP6_STATS_INC(ip6.proterr);
				IP6_STATS_INC(ip6.drop);
				break;
		}
	}

ip6_input_cleanup:
	ip_data.current_netif = NULL;
	ip_data.current_input_netif = NULL;
	ip_data.current_ip6_header = NULL;
	ip_data.current_ip_header_tot_len = 0;
	ip6_addr_set_zero(ip6_current_src_addr());
	ip6_addr_set_zero(ip6_current_dest_addr());

	return ERR_OK;
}


/**
 * Sends an IPv6 packet on a network interface. This function constructs
 * the IPv6 header. If the source IPv6 address is NULL, the IPv6 "ANY" address is
 * used as source (usually during network startup). If the source IPv6 address it
 * IP6_ADDR_ANY, the most appropriate IPv6 address of the outgoing network
 * interface is filled in as source address. If the destination IPv6 address is
 * LWIP_IP_HDRINCL, p is assumed to already include an IPv6 header and
 * p->payload points to it instead of the data.
 *
 * @param p the packet to send (p->payload points to the data, e.g. next
            protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
            IPv6 header and p->payload points to that IPv6 header)
 * @param src the source IPv6 address to send from (if src == IP6_ADDR_ANY, an
 *         IP address of the netif is selected and used as source address.
 *         if src == NULL, IP6_ADDR_ANY is used as source)
 * @param dest the destination IPv6 address to send the packet to
 * @param hl the Hop Limit value to be set in the IPv6 header
 * @param tc the Traffic Class value to be set in the IPv6 header
 * @param nexth the Next Header to be set in the IPv6 header
 * @param netif the netif on which to send this packet
 * @return ERR_OK if the packet was sent OK
 *         ERR_BUF if p doesn't have enough space for IPv6/LINK headers
 *         returns errors returned by netif->output
 */
err_t
ip6_output_if(struct pbuf* p, const ip6_addr_t* src, const ip6_addr_t* dest,
              u8_t hl, u8_t tc,
              u8_t nexth, struct netif* netif)
{
	const ip6_addr_t* src_used = src;

	if(dest != LWIP_IP_HDRINCL) {
		if(src != NULL && ip6_addr_isany(src)) {
			src_used = ip_2_ip6(ip6_select_source_address(netif, dest));

			if((src_used == NULL) || ip6_addr_isany(src_used)) {
				/* No appropriate source address was found for this packet. */
				LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip6_output: No suitable source address for packet.\n"));
				IP6_STATS_INC(ip6.rterr);
				return ERR_RTE;
			}
		}
	}

	return ip6_output_if_src(p, src_used, dest, hl, tc, nexth, netif);
}

/**
 * Same as ip6_output_if() but 'src' address is not replaced by netif address
 * when it is 'any'.
 */
err_t
ip6_output_if_src(struct pbuf* p, const ip6_addr_t* src, const ip6_addr_t* dest,
                  u8_t hl, u8_t tc,
                  u8_t nexth, struct netif* netif)
{
	struct ip6_hdr* ip6hdr;
	ip6_addr_t dest_addr;

	LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);

	/* Should the IPv6 header be generated or is it already included in p? */
	if(dest != LWIP_IP_HDRINCL) {
		/* generate IPv6 header */
		if(pbuf_header(p, IP6_HLEN)) {
			LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip6_output: not enough room for IPv6 header in pbuf\n"));
			IP6_STATS_INC(ip6.err);
			return ERR_BUF;
		}

		ip6hdr = (struct ip6_hdr*)p->payload;
		LWIP_ASSERT("check that first pbuf can hold struct ip6_hdr",
		            (p->len >= sizeof(struct ip6_hdr)));

		IP6H_HOPLIM_SET(ip6hdr, hl);
		IP6H_NEXTH_SET(ip6hdr, nexth);

		/* dest cannot be NULL here */
		ip6_addr_copy(ip6hdr->dest, *dest);

		IP6H_VTCFL_SET(ip6hdr, 6, tc, 0);
		IP6H_PLEN_SET(ip6hdr, p->tot_len - IP6_HLEN);

		if(src == NULL) {
			src = IP6_ADDR_ANY6;
		}

		/* src cannot be NULL here */
		ip6_addr_copy(ip6hdr->src, *src);

	} else {
		/* IP header already included in p */
		ip6hdr = (struct ip6_hdr*)p->payload;
		ip6_addr_copy(dest_addr, ip6hdr->dest);
		dest = &dest_addr;
	}

	IP6_STATS_INC(ip6.xmit);

	LWIP_DEBUGF(IP6_DEBUG, ("ip6_output_if: %c%c%"U16_F"\n", netif->name[0], netif->name[1], (u16_t)netif->num));
	ip6_debug_print(p);

#if ENABLE_LOOPBACK
	{
		int i;
#if !LWIP_HAVE_LOOPIF

		if(ip6_addr_isloopback(dest)) {
			return netif_loop_output(netif, p);
		}

#endif /* !LWIP_HAVE_LOOPIF */

		for(i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
			if(ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
			        ip6_addr_cmp(dest, netif_ip6_addr(netif, i))) {
				/* Packet to self, enqueue it for loopback */
				LWIP_DEBUGF(IP6_DEBUG, ("netif_loop_output()\n"));
				return netif_loop_output(netif, p);
			}
		}
	}
#endif /* ENABLE_LOOPBACK */
#if LWIP_IPV6_FRAG

	/* don't fragment if interface has mtu set to 0 [loopif] */
	if(netif->mtu && (p->tot_len > nd6_get_destination_mtu(dest, netif))) {
		return ip6_frag(p, netif, dest);
	}

#endif /* LWIP_IPV6_FRAG */

	LWIP_DEBUGF(IP6_DEBUG, ("netif->output_ip6()\n"));
	return netif->output_ip6(netif, p, dest);
}

/**
 * Simple interface to ip6_output_if. It finds the outgoing network
 * interface and calls upon ip6_output_if to do the actual work.
 *
 * @param p the packet to send (p->payload points to the data, e.g. next
            protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
            IPv6 header and p->payload points to that IPv6 header)
 * @param src the source IPv6 address to send from (if src == IP6_ADDR_ANY, an
 *         IP address of the netif is selected and used as source address.
 *         if src == NULL, IP6_ADDR_ANY is used as source)
 * @param dest the destination IPv6 address to send the packet to
 * @param hl the Hop Limit value to be set in the IPv6 header
 * @param tc the Traffic Class value to be set in the IPv6 header
 * @param nexth the Next Header to be set in the IPv6 header
 *
 * @return ERR_RTE if no route is found
 *         see ip_output_if() for more return values
 */
err_t
ip6_output(struct pbuf* p, const ip6_addr_t* src, const ip6_addr_t* dest,
           u8_t hl, u8_t tc, u8_t nexth)
{
	struct netif* netif;
	struct ip6_hdr* ip6hdr;
	ip6_addr_t src_addr, dest_addr;

	LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);

	if(dest != LWIP_IP_HDRINCL) {
		netif = ip6_route(src, dest);
	} else {
		/* IP header included in p, read addresses. */
		ip6hdr = (struct ip6_hdr*)p->payload;
		ip6_addr_copy(src_addr, ip6hdr->src);
		ip6_addr_copy(dest_addr, ip6hdr->dest);
		netif = ip6_route(&src_addr, &dest_addr);
	}

	if(netif == NULL) {
		LWIP_DEBUGF(IP6_DEBUG, ("ip6_output: no route for %"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F"\n",
		                        IP6_ADDR_BLOCK1(dest),
		                        IP6_ADDR_BLOCK2(dest),
		                        IP6_ADDR_BLOCK3(dest),
		                        IP6_ADDR_BLOCK4(dest),
		                        IP6_ADDR_BLOCK5(dest),
		                        IP6_ADDR_BLOCK6(dest),
		                        IP6_ADDR_BLOCK7(dest),
		                        IP6_ADDR_BLOCK8(dest)));
		IP6_STATS_INC(ip6.rterr);
		return ERR_RTE;
	}

	return ip6_output_if(p, src, dest, hl, tc, nexth, netif);
}


#if LWIP_NETIF_HWADDRHINT
/** Like ip6_output, but takes and addr_hint pointer that is passed on to netif->addr_hint
 *  before calling ip6_output_if.
 *
 * @param p the packet to send (p->payload points to the data, e.g. next
            protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
            IPv6 header and p->payload points to that IPv6 header)
 * @param src the source IPv6 address to send from (if src == IP6_ADDR_ANY, an
 *         IP address of the netif is selected and used as source address.
 *         if src == NULL, IP6_ADDR_ANY is used as source)
 * @param dest the destination IPv6 address to send the packet to
 * @param hl the Hop Limit value to be set in the IPv6 header
 * @param tc the Traffic Class value to be set in the IPv6 header
 * @param nexth the Next Header to be set in the IPv6 header
 * @param addr_hint address hint pointer set to netif->addr_hint before
 *        calling ip_output_if()
 *
 * @return ERR_RTE if no route is found
 *         see ip_output_if() for more return values
 */
err_t
ip6_output_hinted(struct pbuf* p, const ip6_addr_t* src, const ip6_addr_t* dest,
                  u8_t hl, u8_t tc, u8_t nexth, u8_t* addr_hint)
{
	struct netif* netif;
	struct ip6_hdr* ip6hdr;
	ip6_addr_t src_addr, dest_addr;
	err_t err;

	LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);

	if(dest != LWIP_IP_HDRINCL) {
		netif = ip6_route(src, dest);
	} else {
		/* IP header included in p, read addresses. */
		ip6hdr = (struct ip6_hdr*)p->payload;
		ip6_addr_copy(src_addr, ip6hdr->src);
		ip6_addr_copy(dest_addr, ip6hdr->dest);
		netif = ip6_route(&src_addr, &dest_addr);
	}

	if(netif == NULL) {
		LWIP_DEBUGF(IP6_DEBUG, ("ip6_output: no route for %"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F"\n",
		                        IP6_ADDR_BLOCK1(dest),
		                        IP6_ADDR_BLOCK2(dest),
		                        IP6_ADDR_BLOCK3(dest),
		                        IP6_ADDR_BLOCK4(dest),
		                        IP6_ADDR_BLOCK5(dest),
		                        IP6_ADDR_BLOCK6(dest),
		                        IP6_ADDR_BLOCK7(dest),
		                        IP6_ADDR_BLOCK8(dest)));
		IP6_STATS_INC(ip6.rterr);
		return ERR_RTE;
	}

	NETIF_SET_HWADDRHINT(netif, addr_hint);
	err = ip6_output_if(p, src, dest, hl, tc, nexth, netif);
	NETIF_SET_HWADDRHINT(netif, NULL);

	return err;
}
#endif /* LWIP_NETIF_HWADDRHINT*/

#if LWIP_IPV6_MLD
/**
 * Add a hop-by-hop options header with a router alert option and padding.
 *
 * Used by MLD when sending a Multicast listener report/done message.
 *
 * @param p the packet to which we will prepend the options header
 * @param nexth the next header protocol number (e.g. IP6_NEXTH_ICMP6)
 * @param value the value of the router alert option data (e.g. IP6_ROUTER_ALERT_VALUE_MLD)
 * @return ERR_OK if hop-by-hop header was added, ERR_* otherwise
 */
err_t
ip6_options_add_hbh_ra(struct pbuf* p, u8_t nexth, u8_t value)
{
	struct ip6_hbh_hdr* hbh_hdr;

	/* Move pointer to make room for hop-by-hop options header. */
	if(pbuf_header(p, sizeof(struct ip6_hbh_hdr))) {
		LWIP_DEBUGF(IP6_DEBUG, ("ip6_options: no space for options header\n"));
		IP6_STATS_INC(ip6.err);
		return ERR_BUF;
	}

	hbh_hdr = (struct ip6_hbh_hdr*)p->payload;

	/* Set fields. */
	hbh_hdr->_nexth = nexth;
	hbh_hdr->_hlen = 0;
	hbh_hdr->_ra_opt_type = IP6_ROUTER_ALERT_OPTION;
	hbh_hdr->_ra_opt_dlen = 2;
	hbh_hdr->_ra_opt_data = value;
	hbh_hdr->_padn_opt_type = IP6_PADN_ALERT_OPTION;
	hbh_hdr->_padn_opt_dlen = 0;

	return ERR_OK;
}
#endif /* LWIP_IPV6_MLD */

#if IP6_DEBUG
/* Print an IPv6 header by using LWIP_DEBUGF
 * @param p an IPv6 packet, p->payload pointing to the IPv6 header
 */
void
ip6_debug_print(struct pbuf* p)
{
	struct ip6_hdr* ip6hdr = (struct ip6_hdr*)p->payload;

	LWIP_DEBUGF(IP6_DEBUG, ("IPv6 header:\n"));
	LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP6_DEBUG, ("| %2"U16_F" |  %3"U16_F"  |      %7"U32_F"     | (ver, class, flow)\n",
	                        IP6H_V(ip6hdr),
	                        IP6H_TC(ip6hdr),
	                        IP6H_FL(ip6hdr)));
	LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP6_DEBUG, ("|     %5"U16_F"     |  %3"U16_F"  |  %3"U16_F"  | (plen, nexth, hopl)\n",
	                        IP6H_PLEN(ip6hdr),
	                        IP6H_NEXTH(ip6hdr),
	                        IP6H_HOPLIM(ip6hdr)));
	LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP6_DEBUG, ("|  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |  %4"X32_F" | (src)\n",
	                        IP6_ADDR_BLOCK1(&(ip6hdr->src)),
	                        IP6_ADDR_BLOCK2(&(ip6hdr->src)),
	                        IP6_ADDR_BLOCK3(&(ip6hdr->src)),
	                        IP6_ADDR_BLOCK4(&(ip6hdr->src))));
	LWIP_DEBUGF(IP6_DEBUG, ("|  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |\n",
	                        IP6_ADDR_BLOCK5(&(ip6hdr->src)),
	                        IP6_ADDR_BLOCK6(&(ip6hdr->src)),
	                        IP6_ADDR_BLOCK7(&(ip6hdr->src)),
	                        IP6_ADDR_BLOCK8(&(ip6hdr->src))));
	LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP6_DEBUG, ("|  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |  %4"X32_F" | (dest)\n",
	                        IP6_ADDR_BLOCK1(&(ip6hdr->dest)),
	                        IP6_ADDR_BLOCK2(&(ip6hdr->dest)),
	                        IP6_ADDR_BLOCK3(&(ip6hdr->dest)),
	                        IP6_ADDR_BLOCK4(&(ip6hdr->dest))));
	LWIP_DEBUGF(IP6_DEBUG, ("|  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |\n",
	                        IP6_ADDR_BLOCK5(&(ip6hdr->dest)),
	                        IP6_ADDR_BLOCK6(&(ip6hdr->dest)),
	                        IP6_ADDR_BLOCK7(&(ip6hdr->dest)),
	                        IP6_ADDR_BLOCK8(&(ip6hdr->dest))));
	LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
}
#endif /* IP6_DEBUG */

#endif /* LWIP_IPV6 */
